The present invention relates to novel 1,4,2-diazaphospholidine derivatives, to a process for preparation thereof and to use as catalysts.
Diazaphospholidines, especially species with a P—N—C—N—C sequence in the five-membered ring, are rare and generally occur in moderate yields in reactions which require reactants which are difficult to synthesize and are often associated with the formation of by-products which are either difficult to remove or can only be recycled with very great difficulty back into the production cycle of the reactant(s) (cf., for example, Zhurnal Obshchei. Khimii (1980) 50 (7), 1446-1451; Izv. Akad. Nauk, Ser. Khim. (1996) 7, 1857-1859; U.S. Pat. No. 3,551,527, U.S. Pat. No. 3,980,618, U.S. Pat. No. 3,989,727, U.S. Pat. No. 3,980,618, U.S. Pat. No. 3,965,127, U.S. Pat. No. 3,904,654).
Diazaphospholidines with geminal carbonyl groups and two P—N bonds in the ring are known from phosphorus and sulphur (1980) 8, 27-36.
1,4,2-Diazaphospholidine-3,5-diones, 1,4,2-diazaphospholidine-3,5-dithiones and the corresponding phosphacycles where R2-N=substituent(s) in place of one or both chalcogen atoms are entirely unknown.
2,5-Dihydro-1H-phospholes are often contaminated with the unsymmetrically substituted equivalents, the 2,3-dihydro-1H-phospholes. The latter are of interest as catalysts for isocyanate oligomerization, and so they first have to be freed of undesired constituents such as the 2,5-dihydro isomers before use in the oligomerization reaction.